Download - Simulation & Modelling
Simulation & ModellingSimulation & Modelling
Systems Engineering Training Programme for DRDO Systems Engineering Training Programme for DRDO Scientists at IAT, PuneScientists at IAT, Pune
22ndnd July 2003 July 2003
Lecture-2: Simulation Types, Tools and SimulatorsLecture-2: Simulation Types, Tools and Simulators
Lecture Outline
• Software Simulation & Languages
• Concept of a Simulator.
• Engineering Simulators.
• Basic Philosophy of Simulator Building
• Examples of Software Simulators.
• Examples of Hardware Based Simulators.
Why Software Simulation?
– Software simulation is usually a low cost, quick turn-around time option for most of the design cycles.
– Ability to solve complex mathematical equations (e.g. CFD) enhances the utility of software simulation to the design & development process.
– Availability of fast and powerful digital computers have rendered software simulation quite popular.
– Pure software simulations can come fairly close to real system, as an aid in crucial decision making.
What is Software Simulation?
– Software simulation pertains to solution of a purely mathematical model.
– Software simulation generates system response to inputs, without actual product realization.
– In involves writing a program that is executed on a computer, to create the ‘real’ situation.
– Software simulations can be both “Offline” as well as “real-time” simulation.
Software Simulation Tools
– Software simulation is carried out by programming a digital computer suitably.
– Programming is usually carried out in a higher level language, either general purpose or special purpose.
– Extensive graphic support is needed to set up a software simulation.
– Operating System also plays an important role in setting up a software simulation.
Software Simulation Languages
– General purpose simulation languages are usually not designed for specific needs of simulation.
– FORTRAN, C, C++ etc. are examples of such general purpose languages which can be used for setting up a software simulation.
– These are designed for many different applications and programming effort, to create a specific simulation, can be quite large.
– However, these are highly portable across different computer hardware, Operating System & Compiler, resulting in cost-effective simulations.
Software Simulation Languages
– Special purpose simulation languages are designed keeping in mind, specific needs of simulation.
– These contain a library of pre-defined macros (or “tools”) which minimize overall programming effort.
– CSMP is a popular language for continuous system simulation.
– For discrete system models, GPSS, SIMLIB, ALGOL, SIMSCRIPT II, SIMULA, etc. are used.
– Non-portability is usually the main drawback for these special purpose language, making them costly.
Software Simulation Languages
– Another class of languages, called symbolic language, also find use in setting up simulations.
– These provide a library of mathematical functions which can be put together to create a simulation.
– MATLAB is one such symbolic language that has acquired significant popularity as a simulation language, mainly because of programming simplicity.
– Provision of a variety of tool boxes in MATLAB has made it applicable to a large set of Engg. problems.
Software Simulation in CSMP
Y = INTGRL(IC,x), Y(0) = IC
Y = LIMIT(P1,P2,x)
Y=STEP(P)
Y = EXP(x)
Y = ABS(x)
Y = ALOG(x)
Y = SIN(x)
Y = COS(x)
Y = SQRT(x)
Y = AMAX1(x1, x2, …, xn)
Y = AMIN1(x1, x2, …, xn)
INCON – Initial Conditions
CONST – Constant
PARAM – Parameter
TIMER – Time Interval
PRINT – Printing Variables
PRTPLT – Plotting Data
TITLE – Output Heading
LABEL – Intermediate Headings
END – End of Program
ENDJOB – Task Completion
CSMP provides for following macros.
Example of CSMP Code
• Suspension System - (Step Response)
M
K D
F
X
TITLE SUSPENSION SYSTEM
PARAM D = (5.56,16.9,39.5,56.5)
X2DOT = (1.0/M)*(K*F – K*X – D*XDOT)
XDOT = INTGRL(0.0,X2DOT)
X = INTGRL(0.0,XDOT)
CONST M = 2.0, F = 1.0, K = 400.0
TIMER DELT=0.005, FINTIM=1.5,
PRDEL=0.05, OUTDEL=0.05
PRINT X, XDOT, X2DOT
PRTPLT X
LABEL DISPLACE. VS. TIME
END
STOP
Software Simulation in SIMULINK
Discrete: Unit Delay, Integrator, 0 Order Hold, 1st Order Hold, DTF, DSS, Dfilter, Dzero-Pole
Sources: Constant, Signal Generator, Step, Sine, Chirp, Clock, File, Random No.
Linear: Gain, Sum, Integrator, TFunction, State-Space, Zero-Pole, Derivative, Dot Product
Tool Boxes: Communication, DSP, Control, Fuzzy, System ID, NNET, StateFlow, NCD
Connections: In, Out, Mux, Demux, From, Goto, Data Store/Read, Memory, Enable, Trigger, Ground, Terminator, IC, Subsystem, Selector, Width
Nonlinear: Abs, Math, Trig., Floor, MinMax, Product, Logic, Relation, Sign, Rate Limit, Saturation, Function, …. Etc.
Sinks: Scope, X-Y Graph, Display, File, Stop
SIMULINK provides following functional groups.
Example of SIMULINK Model
• Suspension System - (Step Response)
M
K D
F
X 1
s +2.845s+2002
Transfer FcnStep Scope
Simulation in FORTRAN or C
• Suspension System - (Step Response)
M
K D
F
X
Main Program
Data Structures
Data Communication Strategy
Integration Subroutine
Plotting Subroutine
Flight Simulation
– Flight simulation pertains to solution and visualization of controlled aircraft motion.
– There are many levels at which flight simulation is performed, depending on the need.
– At the lowest end, we have “Design Simulation”, which is a purely mathematical exercise. It contains highly idealized sub-system models.
– Next, is the Engineering Simulator, in which more accurate and detailed models of many sub-systems are available. However, no hardware is included.
Flight Simulation
– “Iron Bird” simulation is the next level of flight simulation wherein a majority of sub-system hardware, excepting aircraft, are integrated with software models.
– “Pilot-in-Loop” simulation caters for man-machine interface development and is usually carried out at number of stages.
– In-Flight simulation is a technique used to check out new sub-system designs (especially Control Laws) on an existing proven aircraft.
– Ground based Real Time Simulation, on a motion platform, is closest to “Flight Simulation” .
Summary of Software Simulation
– Software simulation is a design tool that needs to be configured based on specific needs.
– Computer, Operating System and Languages play an important role in software based simulations.
– Simulator is the system that is capable of performing simulations as per the need.
– Next part of lecture deals with simulator related issues.